This invention relates to a method and apparatus for cutting continuous webs of paper with advance feed holes, which are fed via a feed, after the advance feed tapes or perforated edge strips have been severed, to a transverse cutter arrangement with a non-driven bottom blade and a driven upper blade.
The continuous paper webs for high speed printers and computer systems are cut into single sheets at fixed or variable rates; the cutter has to function cyclically according to its method of operation. During the cutting procedure the paper stands still. The result is that the paper is stressed up to the vicinity of its limit of elasticity at each start up, because a certain period of time also elapses for the cutting process. The transverse cutter, with which the paper web is severed into individual sheets, has to be operated twice in short succession, so that a perforation between the sheets is severed and/or the forms can be cut to the desired dimension.
If a total cycle time is set at 100 msec. for a gross format of 12", upper blade of the cutter stands still for about 75 msec. and is then moved twice in the remaining 25 msec. However, this means that the upper blade which has to carry out a stroke of about 12 mm, has less than 25 msec for two strokes. That means that the blade would have to be moved at a speed of at least 25 meters average per second, if an acceleration distance and a deceleration distance in the working stroke and again in the return stroke did not also have to be taken into consideration. For this reason the speed has to be set much higher.
To date, the conventional eccentric drives have not improved the situation at these speeds, if the necessary speed is not to be obtained by oversizing.